There are a lot of situations where products with moisture control properties, in particular sweat-absorbing properties, are desired. This applies to medical and health-care applications as well as non-medical applications. Herein-below a few such situations are set forth just for illustrative purposes, i.e. without intention to restrict the technical fields where the present invention has utility.
Apart from medical applications which require gas exchange, e.g. pressure to be applied to the skin of a human, such as respiratory masks and wound dressings, there are other medical applications where sweat-absorbing or aqueous fluid-absorbing properties are desired, and non-medical applications (including industrial applications where water-absorbing properties are desired.
For instance there is a need for non-irritating tight seals for adjusting to a part of the human face such as, but not limited to, nasal plugs and ear plugs, which are more skin compatible and/or can be worn for a longer period of time than nasal plugs and ear plugs known to date.
Nasal plugs are used for absorbing aqueous fluids such as, but not limited to, blood, e.g. for stopping nose bleeds or preventing/treating Von Willebrand's disease. The nasal plug expands upon contact with blood to form a soft, non-abrasive sponge that fits the shape of the nasal cavity. Known nasal plugs made from polyvinyl acetate may also incorporate a pharmaceutically active ingredient to act on the source of bleeding. They have the disadvantage of sticking to the walls of the nose after a prolonged period of time, thus reducing easiness of removal and increasing the risk of renewed bleeding. There is a need in the art for nasal plugs made from other polymer materials where adhesion to the walls of the nose can be controlled in time, thus reducing the risk of renewed bleeding and increasing comfort of the patient.
In the field of external as well as in-ear head sets (ear clips) for e.g. ear phones, audio systems and hearing aids, hydrophobic silicones are used that have the disadvantage of not taking up moisture, thus resulting in the ear head set feeling uncomfortable after a limited period of time. Furthermore with moisture accumulation at the ear skin level, the ear head set easily looses stability. There is a need in the art for an ear head set with increased comfort and stability for the wearer.
Standard materials for catheters include hydrophobic silicones, polyvinyl chloride (PVC), and latex rubber. A problem encountered with hydrophobic silicone catheters e.g. for cardiac and other interventional procedures is the gliding of the material during insertion and moving. There is a need in the art for an improved control of gliding of the catheter, especially when moisture of the surrounding tissue is changing with time. The same need is requested for silicone based medical gloves for medical procedures as for example gynecological procedures were a good gliding is requested or for silicone based condoms.
A more specific problem with urinary catheters is mineral encrustation, which occurs when urease-producing bacteria hydrolyze urea to ammonia making the urine more alkaline. The increased pH results in formation and precipitation of calcium- and magnesium-containing crystals. This mineral deposition can block the catheter eyelet and cause pain during extraction. There is a need in the art for a material reducing mineral encrustation of urinary catheters.
Rubber is used to provide stable grip to all kind of handles such as, but not limited to, a bike handle or a part of a wooden saw handle or a steering wheel or a joystick to give a few examples. If these handles are used for a prolonged period of time (e.g. several hours) and/or outdoors, due to a sweat or rain buildup the rubber handle becomes slippery. There is a need in the art for improving grip stability of handles by absorbing sweat or moisture of the handle material.
There is also a need in the clothing industry for example the shoe industry for improving comfort in clothing wearing, e.g. shoe-wearing, by improving both moisture uptake and prevention of bacteria on textile and non-textile regions in shoes.
There is a need in the art for improving moisture uptake on textile products or fibers such as, but not limited to, sport clothes under heavy sweat conditions, including cotton textiles, to prevent the textile from feeling wet or damp after prolonged use, and thus improving comfort of the textile wearer.
There is a need in the industry for body contact belts, and bands such as wristbands that are applied to the skin for a prolonged period of time, to prevent sweat and give persons a comfortable wearing experience. This can be for example for bands applied around the body or the wrist for wearing sensors for e.g. vital sign monitoring.
There is a need in the industry for body contact regions such as (optionally light weight and/or flame retardant) seats like chairs and armchairs in e.g. airplanes, trains, buses, theaters, conference halls that are used for a prolonged period of time to prevent sweat and give persons a comfortable seating experience.
There is a need in the industry for silicone compositions wherein high amounts of polar compounds such as, but not limited to TiO2 powder, are incorporated into the silicone for applications such as, but not limited to, highly reflective polymer products.
There is also a need in the art for anti-condensation layers and sealing materials with good adhesion on all kind of surfaces such as, but not limited to, metal plates used in the building industry indoors and outdoors and most important with the ability to efficiently stop the growth of living organisms such as, but not limited to, bacteria, fungi or algae.
There is a need in the art for a coating with the ability to efficiently stop the growth of waterborne organisms on the surface (in particular the underwater surface) of boats such as, but not limited to, barnacles and mussels, without having the high toxicity of current tin toxins or copper.
There is a need in the art for long-term sterile skin coatings such as, but not limited to, adhesive bandage, keeping skin highly moisturized. For instance there is a need in the art for a sterile adhesive bandage or coating which, after one day will be completely saturated with water and afterwards will keep a stabilized high humidity necessary to minimize scar formation of a recent wound or to minimize the appearance of old wound scars while at the same time stopping bacterial growth.
In the art of drug delivery there is a need for a rubbery material acting as an ion exchanger for positively charged drugs such as, but not limited to, a transdermal nicotine patch wherein the drug can be slowly released from the rubber material. There is a need in the pharmaceutical art for a rubbery material capable of dissolving a non charged polar drug such as, but not limited to, propranolol (a non selective beta blocker). This is not limited to only drug delivery where the drug is positively charged but using positively charged side groups also negatively charged drugs can be implemented.
There is a need in industry for fast sliding materials for transportation e.g. of goods from position A to position B. Traditional transportation systems in warehouses such as robots are limited in their speed. A sliding system making use of a hydrophilic polymer material sliding on a water film is desirable to enable a high speed transportation system.
There is a need in industry for non-sticking, sliding sealing rings. The current sliding sealing rings are based on hydrophobic polymer material and have a tendency to stick or to slide only at high forces. Hydrophilic rubbery polymer materials such as hydrophilic silicones are desirable to secure seal while a thin water film will give a good sliding behavior.
There is a need in the industry for compatibilizers to mix different types of fewly compatible polymers, in particular thermoplastic polymers, into homogeneous polymer blends. Hydrophilic silicones are desirable as an extra component to improve polymer compatibility and control the morphology of the resulting polymer blends.
There is a need in the industry for dispersing agents for hydrophobic silicones and hydrophobic particles that may be present inter alia in pigments and in water based mixtures such as paints, cosmetic compositions, surfactant compositions and coating compositions.
There is a need for medical grade improved adhesion silicone products and compositions for hair care. Water-absorbing hydrophilic silicones are desirable to improve hair adhesion due to the moisture in the material as well as the presence of polar groups.
There is also a need in the industry for fire inhibiting or flame retardant polymer products which are capable of significantly taking up moisture.
There is a need in industry for printing stents for tampon printing that are inert but able to pick up water based materials. Standard silicones are hydrophobic and therefore are not the optimum material for tampon printing to take up water based compounds such as water based inks. Hydrophilic silicones are thus desirable to solve this problem.
There is a need in industry for biocompatible surfaces for medical diagnosis. Hydrophilic silicones are desirable to make it possible to graft amino-acids, peptides and/or antibodies to their surface especially for use in biochemical and medical analysis.
There is also a need in industry for oil barriers in silicone rings for technical equipment. Hydrophilic silicones are thus desirable to efficiently enable oil stopping and act as a barrier.
There is also a need in industry for improved printing stamps with water-uptake capacity.
The molecular design and synthesis of hydrophilic silicone materials is a relatively unexplored area. Still, some hydrophilic silicone materials have been disclosed in the known prior art. For example, patent application US2002/0160139 discloses a surface modified polymer including a surface that is covalently bonded to a surface modifying compound. Formation of the covalent bond between the polymer and the surface modifying compound is achieved by a reaction between an intrinsic functional group that is present in the polymer and the functional group of the surface modifying compound. By using a polymer having an intrinsic functional group, a separate surface activation step is avoided. Thus, the material has a hydrophilic surface while the bulk of the material remains hydrophobic. Accordingly, this material does not allow for the uptake of moisture through the material and moisture can thus not be removed effectively.
WO 2010/095105 discloses, for use in a microfluidic system, a rubber material comprising polar side groups whereby each of the side groups is linked with the polymer chain of said rubber material via a linker comprising at least 6 atoms. The polar side groups may be ionic side groups such as —SO3−. For instance the material may be a silicone rubber modified with 15-20 w % sodium alkene C14-16 sulfonate. The silicone rubber may have a chain length from 1000 to 10000 Si—O units, and the modified silicone rubber may be made by radical addition of ω-alkenylsulfonic acids to siloxane units present in the polysiloxane chain.
For solving these problems, introduction of an alpha-olefin sulfonate surfactant into biocompatible polymers such as hydrophobic silicones, polybutadiene, polybutadiene-containing polymers, polybutadiene-polyethylene oxides copolymers, poly(meth)acrylates, and isobutylene-ethylene glycol copolymers may be especially relevant. However alpha-olefin sulfonate surfactants, although having a vinyl functional group, do not easily mix with the monomer of commercial polymers like polyethylene (PE), polypropylene (PP), polybutadiene, polyisoprene, polystyrene (PS), polyacetonitrile (PAN), silicones, poly(meth)acrylates, polyacrylonitrile, acrylonitrile-butadiene-styrene copolymers (ABS) and styrene-acrylonitrile copolymers (SAN). This incompatibility can be due to differences in boiling points, making these non volatile surfactants nearly impossible to use in gas phase polymerizations. Even under liquid phase polymerization conditions, it is difficult to mix a hydrophilic surfactant containing a sulfonic acid salt with a hydrophobic monomer or pre-polymer.
There are mainly three industrial crosslinking methods for silicone rubbers. Two of them, the peroxide method and the tin salt initiated cross-linking method, do not give medical grade rubbers and can only be used for non medical applications. The third method, based on platinum salt catalyzed cross-linking, gives medical grade rubber. The peroxide or the platinum salt catalyzed polymerizations are based on vinyl groups. A vinyl containing hydrophilic molecule may be desirable to participate into the cross-linking reaction and give hydrophilic silicone rubbers.
For each of the three cross-linking methods, other reactive groups than vinyl groups can participate. In the peroxide cross-linking method, compounds with unsaturated carbon-carbon bonds, like vinyl, allyl, ethynyl, acrylic or methacrylic can be used. In the tin salt catalyzed cross-linking method, only hydrophilic molecules with hydrolysable silane groups can be used. For the platinum salt catalyzed cross-linking method, vinyl, allyl and ethynyl groups are preferred.
Only in a special case like the suspension polymerization of vinyl chloride in water, can the hydrophilic surfactant be dissolved in a part of the reaction mixture (water) and thus incorporated into the main polymer. However polyvinyl chloride is not regarded as a skin-compatible polymer.
In addition, as outlined hereinabove it is desirable for the candidate material to be easily transformed into a foam and/or to be easily applied in the form of a coating with good adhesion on various types of polymeric and non-polymeric materials.
In front of the above mentioned prior art, there is still a need for a material with hydrophilic bulk properties both in bulk, as a foam or as a coating for use as an aid in moisture control and/or in controlling growth of living organisms and microorganisms.